Interface sensors with skin piezo-thermic transduction enable motion artifact removal for wearable physiological monitoring

Abstract

Accurate measurements on physiological parameters using wearable monitoring devices during physical exercises are essential for personal healthcare and rehabilitation training, but still challenging owing to various motion artifacts (MA) caused by the interfacial dynamic change between wearable sensors and human skin. Here, we propose an interface sensor to detect noncontact proximity and contact pressure between wearable sensors and human skin. The interface sensor employs natural piezo-thermic transduction of human skin and enables direct interfacial proximity/pressure detection by using simple thin-film thermistors to detect the interfacial thermal field change. We develop a wearable watch-type heart rate (HR) monitor utilizing interface sensors to remove MA for a photoplethysmography (PPG) sensor through adaptive filtering. To validate the method, we conduct experiments for multiple subjects, who carry out HR monitoring using the wearable device while doing various physical exercises. The PPG-based HR estimations are corrected through MA removal using interface sensors and compared with that using conventional accelerometer-based MA removal. The experimental results verify that the interface sensors capture the interfacial dynamic change between the PPG sensor and skin better, and obtain more accurate HR estimations during irregular and muscle strength exercises. Utilizing natural transduction of human skin and simple thermometry, the interface sensor provides an advantageous way to overcome MA for wearable monitoring devices during physical activities and thus broadens wearable monitoring applications.